title: Effects of dopaminergic modulation on automatic semantic priming: a double-blind study.
abstract: BACKGROUND
  Enhanced automatic spreading of activation in the semantic network has been suggested to underlie formal thought disorder in patients with schizophrenia, but it is not clear how this relates to the dopaminergic dysfunction implicated in the disorder. Previous studies on dopaminergic modulation of priming in healthy volunteers have focused on controlled rather than automatic processes. The present study aimed to examine the effects of both a dopaminergic agonist and a dopaminergic antagonist on semantic priming while minimizing the contribution of controlled processes.
  
  
  METHODS
  We investigated the effects of levodopa (L-Dopa; 100 mg), haloperidol (2 mg) and placebo on priming in healthy participants within a randomized, double-blind, crossover design. We used a pronunciation priming task with word triplets; the middle word was an ambiguous word, whereas the first word of the triplet served to provide either a congruent, incongruent or unbiased context for the target word. Two stimulus onset asynchronies (SOA) were used: 150 ms and 750 ms.
  
  
  RESULTS
  The study involved 34 participants. At an SOA of 150 ms, L-Dopa accelerated responses to incongruent targets and subordinate targets of ambiguous words, whereas haloperidol was associated with faster responses in congruent contexts and dominant targets. At an SOA of 750 ms, haloperidol accelerated responses to subordinate targets.
  
  
  CONCLUSIONS
  Modulations in the relative magnitude of priming according to substance and condition rather than absolute priming were assessed.
  
  
  CONCLUSIONS
  Effects of L-Dopa on automatic priming processes appear to be different than those on controlled processes. Our results are consistent with those of studies on semantic priming and the effects on antipsychotics in patients with schizophrenia.
authors.affiliation: The University Medical Center Hamburg-Eppendorf, Department of Psychiatry and Psychotherapy, Hamburg, Germany.
authors.forename: Christina
authors.initials: C
authors.lastname: Andreou
authors.affiliation: The University Medical Center Hamburg-Eppendorf, Department of Psychiatry and Psychotherapy, Hamburg, Germany.
authors.forename: Kristina
authors.initials: K
authors.lastname: Veith
authors.affiliation: 1st Department of Psychiatry, Aristotle University of Thessaloniki, Thessaloniki, Greece.
authors.forename: Vasilis P
authors.initials: VP
authors.lastname: Bozikas
authors.affiliation: The Department of Psychology, University of Hamburg, Hamburg, Germany.
authors.forename: Tania M
authors.initials: TM
authors.lastname: Lincoln
authors.affiliation: The University Medical Center Hamburg-Eppendorf, Department of Psychiatry and Psychotherapy, Hamburg, Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Moritz
mesh_terms: D000328:Adult; D018592:Cross-Over Studies; D004298:Dopamine / Q000378:metabolism; D015259:Dopamine Agents / Q000494:pharmacology*; D018492:Dopamine Antagonists / Q000494:pharmacology*; D004311:Double-Blind Method; D005260:Female; D006220:Haloperidol / Q000494:pharmacology*; D006801:Humans; D007980:Levodopa / Q000494:pharmacology*; D008297:Male; D010364:Pattern Recognition, Visual / Q000187:drug effects / Q000502:physiology; D011930:Reaction Time / Q000187:drug effects; D011932:Reading; D060865:Repetition Priming / Q000187:drug effects* / Q000502:physiology; D012660:Semantics; D013060:Speech / Q000187:drug effects / Q000502:physiology; D055815:Young Adult
chemical_list: D015259:Dopamine Agents; D018492:Dopamine Antagonists; D007980:Levodopa; D006220:Haloperidol; D004298:Dopamine